ACTIVITY OF PLANT ESSENTIAL OILS AGAINST GIARDIA DUODENALIS

Giardia duodenalis (synonyms: Giardia lamblia and Giardia intestinalis) is a common flagellate, zoonotic protozoan causing the diarrheal disease giardiasis. There is little information about the essential oils of plants found in Thailand against this parasite. We aimed to determine the efficacy of essential oils of the following plants against G. duodenalis: Syzygium aromaticum, Zingiber officinale Roscoe, Alpinia galanga, Litsea cubeba, Illicium verum, Zanthoxyluni rhetsa, Citrus x aurantifolia, Citrus hystrix, Citrus reticulata, Odium basilicum and Ocitnum africanum, using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium reduction assay. It was found that essential oils of C. x aurantifolia was the most effective against G. duodenalis with IC50 = 6.96 ± 0.13 μg/ml, followed by L. cubeba with IC50 = 60.67 ± 0.82 μg/ml in dose-dependent fashion. The other essential oils had no efficacy against G. duodenalis, suggesting they may contain fewer antigiardial constituents. Future studies are needed to elucidate major active constituents of these essential oils and prove their efficacy and safety for treatment of G. duodenalis.